Introduction of the liability indicator into complex segregation analysis to allow for effects of age, sex, and other individual variables, and analysis of pyloric stenosis, neural tube defects, limb reduction abnormalities, oral clefts, and other diseases important in genetic counseling. Development of a program for risks based on complex segregation analysis of a quantitative trait, affection status, liability indicator, and combinations of the first or last two. Prediction of risks for the above diseases as an aid to counselors and demonstration of the precision and specificity which this approach brings to genetic counseling.